Procedural Rougness texture
It depends if you mean roughness as a 2D effect or 3D effect.

For 2D roughness you can use a Noise (or this kind of texture) as a factor in a mix between a glossy and a non glossy material:



For 3D roughness you need to plug a Noise (or this kind of texture) into a Bump node that you plug into the Normal sockets of your nodes. Here I've mixed 2 Noise Texture nodes into a MixRGB (try Overlay or Darken or Lighten mode) in order to have some smoother areas.



If you're not fully procedural and use an Image Texture:

In the case of a 2D effect, if you use an Image Texture you can create something without any unwrap, I guess it's the quickest way:


Prepare your dirt texture (a simple black and white jpg is ok).
Create this nodes setup: Texture Coordinate (Object output) > Mapping > Image Texture > ColorRamp > Factor socket of a Mix Shader.
In the Image Texture, load your dirt image, choose Box instead of Flat so that the texture will be projected all around the object. You may need to play with the Blend factor to avoid any seam effect.
In the Mix Shader, plug the 2 materials, the one that is supposed to be the glossy and the rough one.
You can play with the Location and Scale of the Mapping node, but don't play with the Rotation if you want to avoid stretching.





In the case of a 3D effect, same setup on the left, then:


Plug your Image Texture node into the Height socket of a Bump node.
Plug the Bump into the Normal sockets of your Diffuse and Glossy nodes.
Here I've used a (Math) Multiply node instead of a ColorRamp. - Play with the Strength of the Bump to increase the 3D effect.